1. Field of the Invention
The present invention relates to a measuring device subjected to gravitational forces and including at least one laterally oscillating, pendulously suspended support structure for supporting, e.g., an optical device. In particular, the present invention relates to a suspension for such a device.
2. Description of the Prior Art
In many scientific and technical applications, the gravity force acting on a measuring system plays not inconsiderable role. In many cases, the action of the gravity force is used directly or indirectly for solving a measurement problem Inclinometer, horizon sensor, accelerometer, leveling devices are examples of measuring devices influenced by gravitational forces. In particular, it is often necessary to precisely align horizontally and/or vertically a measuring device, a display device, an optical device and the like. In particular, optical devices for projection of marks over large distances put high demands to a leveling device in order to keep a projection error over a large distance as small as possible. For some time, in constructional industry and in building technology, apparatuses, which contain optical devices for transmitting marks over large distances, e.g., with a light beam, in particular, with a laser beam, are used. With the help of an optical device, which is contained in an apparatus, a laser beam is splitted, e.g., in two or three laser beam components extending, respectively, perpendicular to each other. With such an optical device, an apparatus for displaying right angles and for laying out horizontally and/or vertically extending marks can be formed.
The prior art discloses different solutions for aligning a laser beam manually or automatically in order to insure an exact horizontal and/or vertical course of a laser beam in case of uneven surfaces. One of the known solution consists in that a support plate for a light source and an optical device, which is arranged in the housing of an apparatus, is manually adjusted horizontally and/or vertically in a desired manner with set screws and level indicators, e.g., bubble or water levels. This solution is constructively relatively expensive. Besides, manual adjustment is laborious and often cannot be effected with a desired precision. The adjustment can be simplified and a high adjustment precision can be achieved by the automatization of the adjustment process, e.g., by providing servomotors connected with the level indicator. However, this solution is associated with relatively high costs, connected with the provision of necessary mechanical and electronic means, and increases the overall cost of the measuring apparatus. In addition, leveling devices equipped with servomotors require a relatively large mounting space and, therefore, are used primarily with large precision apparatuses, e.g., with rotating constructional lasers.
U.S. Pat. No. 5,459,932 discloses a laser indicator which emits at least two mutually perpendicular laser beam. The disclosed indicator is used for transmission of horizontal and/or vertical marks or right angles. With this apparatus, e.g., components can be exactly aligned and controlled horizontally and vertically or arranged at a right angle. The apparatus has relatively small dimensions. The action of the leveling device for horizontal and/or vertical alignment of the laser beams is based on the use of gravitational forces. To this end, the light source and the optical device are arranged on a platform which is attached, in a pendulum-like manner, to a wire suspended from the apparatus housing. The pendulously suspended platform has two lateral degrees of freedom and, thereby, can by itself compensate unevenness of the support surface of the apparatus due to action of the gravitational forces. Damping of the pendulously suspended platform is effected, e.g., with a magnetic means. To this end, magnetized elements arranged on the platform cooperate with magnets arranged in the apparatus housing in the vicinity of the platform. To prevent breaking of a relatively brittle wire suspension under impact loads, at least one spring element is provided between a point, at which the wire is attached to the housing, and a point at which it is connected with the platform. The spring element, e.g., a coil spring, damps all of the impacts applied to the housing and reduces the danger of the wire suspension being broken. The spring element can be serieusly connected with the wire suspension but also can be used instead of the wire suspension. For power supply, there are provided thin conducting wires which connect a power source arranged in the housing with the light source. The conducting wires have a relatively small mass and are arranged in such a way that their influence on the pendulously suspended platform is minimal. Nevertheless, the stiffness of the wire suspension and the mass of the conducting wires create a torque which prevents an exact horizontal and/or vertical alignment of the platform. The insignificant position errors are compensated with optical means.
Accordingly, an object of the present invention is to improve the apparatus or device described in the above-mentioned U.S. Patent so that the susceptibility of the pendulously suspended platform to impacts is further reduced. A further object of the present invention to prevent, to a most possible extent, interfering oscillation mods such as particularly occurring in wire suspensions. The pendulous suspension of a platform, which supports the light source of the laser and the optical device, should be modified so that preconditions for reducing the influence of the torque of the conducting wires on the pendulous suspension are created. The modified pendulous suspension should be capable of being produced in a simple and cost-effective manner.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a measuring device subjected to gravitionaly forces and including at least one laterally oscillating, pendulously suspended, support structure for supporting at least one of measuring means and optical means, and means for suspending the support structure and including at least one hinge formed as a tape hinge. Tape hinges have, as a result of their lateral tensioning under the action of impact loads, a greater rigidity than a springy pendulous wire or thread suspension a cross-section of which approximates a point. By forming the hinge as a tape hinge, a bendable region is formed in the hinge which is characterized by a fixed laterally extending neutral axis in a narrow predetermined longitudinal region of the hinge. Further, with regard to available materials, a greater selection of material exists for tape hinges than is the case with wire or thread suspensions. Tape hinges despite their relatively greater rigidity, have a high flexibility and a small base stiffness.
During manufacturing of the tape hinge, the oscillation damping aspect is taken care of to a certain degree by the geometrical design of the hinge section. Thereby, additional damping means, e.g., magnetic means, can be reduced in size. The technology for producing the tape hinges is cost-effective and has proved itself. The articulation region of the suspension can be prefabricated with a reproducible stiffness and need not be first formed during the mounting, as is the case with suspension wires, which may result, dependant on the quality of the mounting, in that the hinge stiffness would differ from hinge to hinge. Because the hinge link is prefabricated, it can be easily mounted in the device.
In particular, tape hinges are suitable for a completely automatic mounting, which further reduces manufacturing and assembly costs of a device equipped with a leveling device according to the present invention.
The suspension can, e.g., include a rubber-like material at least in the articulation region. According to a preferred embodiment of the present invention, which is particularly adapted for a mass production of the suspension, the tape hinge includes plastics or a material compound, in particular, a plastic compound with rubber characteristics. E.g., as a plastic material, polymers such as polyolefine, polypropylene, polyvinyl compounds, or products of polycondensation, such as, e.g., polyamide, and/or their co-polymers can be used. In the articulation region, a tape hinge, which is formed of a thermoplastic material or a material compound with rubber characteristics, has a wall thickness from about 5 xcexcmm to about 400 xcexcm. The longitudinal extent of the articulation region of such tape hinges is smaller than 3 mm.
While a tape hinge can, e.g., be produced as a one-piece part by injection-molding, there is also exists a possibility to form the hinge of several parts. In this case, the hinge has a band-like section and two sections surrounding the band-like section at its opposite ends and having a greater thickness than a thickness of the band-like section. The surrounding sections can be formed of the same material as the band-like section or of a different material. The two surrounding sections serve as suspension or connection regions.
In an advantageous embodiment of the present invention, the tape hinge is provided with conducting wires which serve for supplying power to components supported on the pendulously suspended platform and/or serve as signal lines. Because the power lines or signal lines are connected with the hinge, preferably, are integrated therein, separate conducting wires, the moment of which can influence the leveling function, are eliminated. The advantage of this consists in that expensive compensation means, which is required, e.g., in case of optical devices, can be dispensed with.
It is advantageous when the suspension includes two serieusly connected tape hinges the articulation regions of which are pivoted relative to each by 90xc2x0. In this embodiment of the inventive suspension, the tape hinges are connected with each other in a manner of a universal coupling, and the serieusly connected tape hinges cover both lateral swinging possibilities. Both hinges can be formed as identical separate hinges connected with each other and pivoted relative to each other by 90xc2x0. According to a further embodiment of the invention, both hinges can be formed as a one-piece part.
According to a further embodiment of the invention, the suspension includes at least two serieusly connected frame structures hingedly connected with each other by at least one tape hinge. The frame structures can be reliably secured in the housing and provide a relative large surface for connection with the support structure, i.e., the platform. They have a vertical orientation and provide sufficient space for measuring and optical means arrangeable on the pendulously suspended platform.
For effecting a cardanic suspension, there are provided three serieusly connected frame structures, with each two adjacent frame structures being connected with each other by tape hinges. The hinged connection of the first and second frame structures is pivoted relative to the hinged connection of the second and third frame structures by 90xc2x0. The hingedly connected frame structures are advantageously formed as a one-piece plastic part which, advantageously, is produced by injection-molding.
The suspension according to the present invention for use in a measuring device subjected to gravitational forces can have many applications where a gravitational force influences the measurement. It is particularly suitable for a leveling devices based on the use of a gravitational force for aligning the device or its measuring system precisely in a desired direction circumferentially. The inventive suspension is particularly suitable for apparatuses the leveling device of which is formed for horizontal and/or vertical alignment of a light source arranged on a pendulously suspended platform on which, if necessary, an optical beam splitter connected with the light source can be arranged. It is particularly suitable for multi-axes laser indicator devices which emit at least two mutually perpendicular laser beams and are used, e.g., for marking and controlling of exact horizontal and/or vertical alignment of constructional parts and for display of right angles.